1. Field of the Invention
This invention relates to reprogrammable “field programmable gate arrays” (FPGAs). More specifically, the invention is a system that is integrated on a reprogrammable FPGA that can mitigate the effects of single event upsets such as those induced in a reprogrammable FPGA operating in a radiation environment.
2. Description of the Related Art
A “field programmable gate array” or FPGA is a semiconductor device containing programmable logic components and programmable interconnects. The programmable logic components can be programmed to duplicate the functionality of basic logic gates or more complex combinatorial functions such as decoders or simple math functions. In most FPGAs, these programmable logic components or logic blocks also include memory elements which can be simple flip-flops or more complete blocks of memory.
A reconfigurable or “reprogrammable” FPGA is an FPGA that can be changed to form different logic functions on demand. The logic circuits in a reprogrammable FPGA generally employ bi-stable data storage elements within which the logic configuration data is stored. A data storage element's “state” (i.e., either a logical “one” or logical “zero”) determines whether or not the “device” (e.g., logic, configuration interface gate, etc.) connected to the data storage element's output is either on or off. In that way, blocks of logic elements are connected/disconnected to thereby configure the logic circuit. Selectively changing the data stored in some of the data storage elements allows one to reconfigure the logic circuits. Such reconfigurable logic circuits offer a significant advantage over one-time programmable “firm” logic circuits in that the hardware can be changed even after the digital system has been deployed for many years.
The versatility offered by reprogrammable FPGAs make them ideally suited for a variety of applications to include aerospace. However, aerospace applications often involve environments where radiation is present. Radiation can induce an error in a reprogrammable FPGA known as a “single event upset” (SEU). SEUs can be defined as radiation-induced errors in microelectronic circuits caused when charged particles lose energy by ionizing the medium through which they pass leaving behind a wake of electron-hole pairs. SEUs are transient soft errors, and are non-destructive. Unfortunately, reprogrammable FPGAs are very susceptible to SEUs.
Currently, systems using reprogrammable FPGAs that will be exposed to radiation are designed using radiation tolerant components for the mitigation of SEUs. These radiation tolerant components are in addition to the reprogrammable FPGAs configured for a user application. However, requiring additional radiation tolerant components for SEU mitigation increases the complexity of the overall system design, increases the number of components, requires a greater amount of board space, is more expensive, requires more power for system implementation, and reduces overall system reliability.